The heavy-duty gear burnishing and honing machine of the present invention may have an adjustable duty cycle, and it is capable of finishing gears of various sizes. The rotational speed of the finishing gears, which do the burnishing or honing, is controlled independently of an oscillatory reciprocating motion that is applied to the workpiece gear so that precisely controlled surface finishes can be achieved on hardened gears. High machine speed and low load with abrasive gears provides more of a honing action while a slow machine speed and high load with hardened gears, made with M-2 tool steel, for example, provides more of a burnishing action. A high relative reciprocating speed relative to the rotating speed with a hunting tooth effect provides a uniform wear pattern across the workpiece tooth profile. If there is oscillation, its frequency, the pressure of the finishing gears upon the workpiece gear, the construction of the finishing gears and whether or not they have any hardened materials applied to their surface such as carbide or diamond containing materials are the important factors. In this document, therefore, when the term "burnishing" is used, it is to be understood that the term includes both burnishing and honing.
The versatile heavy-duty honing and burnishing machine of the present invention is capable of handling a large variety of gear sizes. The machine has an adjustable duty cycle and the pressure applied by the burnishing gears on the workpiece gear is adjustable over a wide range also which makes the machine suitable for burnishing soft gears as well as hard gears. The burnishing gears are wider than the workpiece gear so that the workpiece gear can be burnished anywhere along the full width of the burnishing bears, which maximizes life of the burnishing gears. Operating the gear burnisher at high load and low speed on a short duty cycle will remove scale due to heat treatment and minor nicks prior to gear inspection.
With a short duty cycle, it is generally best to use special burnishing gears in the machine that will provide some sliding over the complete tooth profile. This can be accomplished by utilizing one burnishing gear which has a high operating pressure angle and a second burnishing gear which has a low operating pressure angle, as shown and described in pending United States patent application Ser. No. 152,446, now U.S. Pat. No. 4,305,190 assigned to the assignee of the present invention, and filed May 22, 1980 in the name of Henry J. Flair. Reversing rotation of the burnishing gears approximately half way through the duty cycle will reverse the direction of sliding action of these gears above and below the two pitch lines which will provide an appreciably improved surface finish.
Large swage type nicks on the workpiece gear generally require a relatively longer duty cycle, more sliding action, possibly the use of coolant, and if an abrasive honing gear is used, a reduced loading. More uniform sliding action can be accomplished by reciprocating the workpiece gear at a high rate while rotating the burnishing gear at slow speeds in order to achieve a reversing dead-spot hunting effect. Rotation over two revolutions of the burnished gear assures that the short reversing dead-spot will be subject to near peak velocity on the second revolution, and in this way, the full profile of all gear teeth of the workpiece gear will be subjected to a relatively uniform sliding action. High reciprocating rates of the workpiece gear tends to minimize the need for using both high operating pressure angle and low operating pressure angle burnishing gears on the type described in the aforementioned prior United States patent application Ser. No. 152,446.
Reliable loading, guaranteed gear engagement, assured gear discharge and immunity to abrasives are all essential to minimizing maximum down times and maximizing daily production rates. A pressure arm is pivoted so that it can be swung in the direction of the discharge chute to a retracted stop position which positions the driven burnishing gear so that it will prevent a new workpiece gear from passing through the burnishing station without stopping. This position of the driven burnishing gear also insures that this burnishing gear will drive the workpiece gear toward the discharge chute in a positive manner, instead of kicking it out as the pressure arm and the driven burnishing gear swings away from the discharge chute, in the manner shown and described in prior U.S. Pat. No. 2,321,800, issued May 30, 1967 in the name of Gunther Rosendahl, which patent is assigned to the assignee of the present invention.
When the workpiece gear is discharged by being propelled by the driven gear out of the burnishing station, the workpiece gear rides over the top of the idler burnishing gear which is adjacent the discharge chute and which has its rotation stopped by a controllable brake. A proximity switch senses the motion of the workpiece gear down the discharge chute and results in a control signal being generated which allows a new gear to be sent down the input chute. The burnishing cycle does not progress at high speed and high pressure until after the burnishing gears have engaged the new workpiece gear. If for some reason the new workpiece gear is not engaged by the pivotable driven burnishing gear on the first attempt, the pressure arm will pivot the driven gear back to its withdrawn position and will reverse and come in for a second try at attempting to engage the new workpiece gear.
The engagement cycle for the driven burnishing gear with a workpiece gear is under the control of a proximity sensor located at a fixed position on the machine. A pair of spaced-apart metallic washers are mounted to move with the pivotable pressure arm that carries the driven burnishing gear and as the two washers move towards the proximity sensor, the pressure arm pivots downwardly and the driven burnishing gear approach the workpiece gear. When the first washer moves past the proximity sensor, air pressure to the air cylinder that controls the pivoting of the pressure arm and the driven burnishing gear is turned off under control of the sensor as the teeth of the driven burnishing gear engage the teeth of the workpiece gear. When the teeth of the burnishing gears are in engagement with a workpiece gear of the proper pitch diameter, the second sensing washer will be sensed by the proximity sensor which causes the air cylinder to be again actuated so to apply the correct amount of burnishing pressure to the workpiece gear.
However, if the workpiece gear is undersize, the proximity sensor will lose the signal it received from the second washer as the second washer drops past the proximity sensor, which indicates to the control panel that an undersized gear is present. The machine also may be automatically shut off if desired. In the event that the proximity sensor does not sense the second washer, another light on the control panel may indicate that the workpiece gear is oversized and is not engaged by the burnishing gear. In this case the pressure arm will recycle for a second attempt, and if this attempt is unsuccessful, the machine will be turned off.
The reciprocating action of the workpiece gear across the burnishing gears is obtained through a very simple mechanical arrangement of leaf springs which support a C-shaped frame and live-center face pads, which support and take the thrust of the workpiece gear. This mechanical arrangement eliminates the need for sliding gibs which are subject to excessive wear in the presence of abrasive particles that result when a honing action is taking place. All bearings in the machine preferably have their seals flushed periodically with an automatic lubrication system in order to keep abrasives out of the bearings.